Means and method of manufacturing metallized electrical capacitors



Nov. 17, 1959 w. DUBILIER 2,913,647

MEANS AND METHOD OF MANUFACTURING METALLIZED ELECTRICAL CAPACITORSOriginal Filed June 25, 1951 2 Sheets-Sheet 1 I N V EN TOR. M1 4 MM005/1 we Nov. 17, 1959 Original Filed June 25, 1951 W. DUBILIER MEANSAND METHOD OF MANUFACTURING METALLIZED ELECTRICAL CAPACITORS 2Sheets-Sheet 2 g w/miw/Ai i IN V EN TOR. l V/zu/w flue/z A5? BY w. 401%147 Ol Vf V United States Patent MEANS AND METHOD OF MANUFACTURINGMETALLIZED ELECTRICAL CAPACITORS William Dubilier, New Rochelle, N.Y.,assiguor to Cornell-Dubilier Electric Corporation, South Plainfield,N.J., a corporation of Delaware 1 Claim. (Cl. 317-260) The presentinvention relates to methods of and means for manufacturing electricalcapacitors of the type comprising a single strip of metallized paper orequivalent flexible dielectric material wound on a mandrel into aconvolute spiral unit, said strip having been patterned preparatory tothe winding thereof into the final capacitor unit by electricallyburning away or evaporating a portion of the metal coating along a wavyor zig-zag line of progressively increasing pitch, in such a manner thatsuccessive electrode portions of the coating on opposite sides of theinsulating zig-zag line are located in substantial registry one abovethe other in the rolled final unit, so as to effectively cooperate aselectrodes of opposite polarity of the capacitor.

This application is a division of my application Serial Number 233,314,filed June 25, 1951 and which has issued as US. Patent No. 2,671,157.

In a method of this type of manufacturing electrical capacitorsheretofore employed, the branding or patterning is usually eifected bypassing the metallized strip, preparatory to its winding into the finalcapacitor unit, over a wheel provided on its periphery with a raisedportion or pattern of the required zig-zag shape, and applying asuitable electric potential difference between the wheel and metalcoating of the paper base or other insulating strip.

It will be appreciated that this known method requires the use of adifferent patterning wheel for each size or type of capacitor and,furthermore, that the wheels become impracticable for the larger sizesof capacitors, owing to the fact that the Wheels necessary will becometoo bulky and unwieldy to use and incidentally also very costly tomanufacture.

The present invention has for its primary object to effect improvementsin the known methods of patterning a metallized insulating strip,preparatory to its winding into a capacitor unit, whereby the largersizes of ca pacitors having relatively high capacitance values can bereadily manufactured.

Another object is to enable the capacitance value of a capacitor of theabove type to be controlled roughly during the patterning of themetallized strip, to thereby render it unnecessary to provide apatterning wheel for each size of capacitor.

Still another object is to control the capacitance within a relativelyclose tolerance and by a simple expedient during the patterningoperation.

The invention will be better understood from the following detaileddescription of a few practical embodiments considered in conjunctionwith the accompanying drawings, forming part of this specification andwherein:

Fig. 1 illustrates diagrammatically a simple patterning apparatuscomprising a pair of patterning wheels and constructed in accordancewith the principle of the invention;

Fig. 2 shows the patterning wheels of Fig. 1 having their peripheralsurfaces developed into a plane;

Fig. 3 shows one of the masks of Fig. 1 developed into a plane;

Fig. 4 shows a portion of a patterned paper strip obtained by means ofapparatus according to Figs. 1 to 3;

Fig. 5 illustrates diagrammatically a modified form of patterningapparatus according to the invention;

Figs. 6 and 7 illustrate further modifications of multiple wheelpatterning devices constructed in accordance with the principle of theinvention;

Fig. 8 illustrates a method of controlling or adjusting the capacitanceof a single-paper capacitor according to the invention; and

Fig. 9 shows an improved drive for operating the controlling maskembodied in Figs. 1 and 5.

Like reference characters identify like parts throughout the differentviews of the drawings.

While the invention will be described in the following with specificreference to metallized paper capacitors, the term metallized paper isintended to include other flexible insulating materials, such assynthetic plastics, coated with a thin metallic layer in any suitablemanner.

With the foregoing and further objects in view, as will become apparenthereafter, a method of manufac- 'ture according to one feature of thepresent invention comprises passing a single strip of metallized papersuccessively over the shaped peripheries of two or more patterning orbranding wheels each of which acts electrically to burn away orevaporate a portion of the metal coating along a zig-zag line ofprogressively increasing pitch, the individual wheels being caused toact simultaneously or sequentially on different parts of the length ofthe strip. By the proper design of said zig-zag patterns of the wheels,successive electrode portions of the coating on opposite sides of thedemetallized zig-zag line will be located in substantial registry oneabove the other in the final capacitor unit obtained by winding thepatterned strip into a convolute spiral, said electrode portions beinginterconnected alternately in two groups constituting the poles of thecapacitor.

The progressive increase in pitch of the demetallized zig-zag linecontinues from wheel to wheel, in such a manner that, if, for example,there are n wheels of equal diameter, the resultant demetallized zig-zagline on the strip will be equivalent to a line which would be producedby a single wheel of n times the periphery or diameter and having araised peripheral zig-zag pattern or projection of progressivelyincreasing pitch throughout.

It is thus possible to effect a coarse adjustment of the capacitancevalue of the capacitor by varying the number of patterning wheels inefiective use. Risk of shortcircuiting electrode portions, connected toopposite poles of the capacitor, owing to inaccurate registration of thepatterns produced by two consecutive wheels, may be avoided by removingor burning away a small area of the metal coating at the end of thepattern produced by one wheel and/ or at the beginning of the patternproduced by the next following wheel.

The operation or control of the individual Wheels may be effected byinterposing a mask or masks between the wheel peripheries and themetallized strip to be patterned, by interrupting the electric currentsupply to the wheels by means of a suitable switching arrangement, or bymechanically separating the metallized strip from the peripheries of thewheels. These controls may be used individually, or in combination, tocope with any exist ing conditions and requirements in producing a finalpatterned strip suitable for producing a capacitor of desired size orcapacitance.

A further feature of the present invention relates to a method ofadjusting the capacitance value of a capacitor produced by winding asingle metallized and patterne'd strip of the type referred to above.According to this feature, the patterning is rendered ineffective overa. length of the strip dependent upon the desired adjustment by burningaway a portion of the coating along a line which 'lies substantiallyparallel to the length of the strip and intersects the demetallizedZig-zag line, so that there will be no overlap or effective capacitancein such a part of the strip between the electrode portions connected tothe opposite poles of the capacitor.

Referring more particularly to Fig. 1 of the drawings, numerals a and Nbrepresent two patterning or branding wheels, 12 is a web or strip ofmetallized paper passing from a supply roll 13 to a winding mandrel ortake-up roll 14 over the peripheral surfaces of the wheels 10a and ltib.With the arrangement indicated in the drawings, the metallized surfaceof the paper is downwards so that it is in contact with the outerperiphery of the wheels Mia and 10b and in passing over guide rollers15a, 15b, 15c and 15d makes contact with the wheels en route.

In the preferred embodiment of the apparatus, the rollers 15a, 15b, 15cand 15d are advantageously connected to ground or the frame of themachine and the patterning wheels 10a and 10b are mounted in insulatingmaterial or bushings so that they may be connected to a high tensionside of a voltage source it, such as a direct current voltage generatoror rectifier power supply, through a suitable high ohmic limitingresistance 17 and by way of slip rings 20a and Ztlb and sliding brushesor the like, to obtain the requisite burning potentials between thepattern on the wheel surfaces and the metallized coating on the strip12. The low tension side of the source 16 is shown grounded or connectedto the frame of the machine to close the electric circuit and both thegenerator 16 and limiting resistance 17 are suitably by-passed by acapacitor 18, in a manner customary with branding or demetallizingdevices of this type. The auxiliary rollers 21a, 21b, 21c and 21d serveto maintain the paper strip 12 in close contact with the surfaces of therollers 15a, 15b, 15c and 15d, which in turn serve to provide adequatecontact between the raised patterns of the patterning rollers 10a and10b and the metallized coating.

Suitable driving means (not shown) are provided, whereby the strip 12 ispulled from left to right as indicated by the arrows a in the drawing.For this purpose, any convenient drive may be employed, such, forexample, as driving the take-up roller 14 by an electric motor orpassing the strip 12 between separate friction or driving rollers,whereby it is pulled along at a constant speed. In addition, thepatterning wheels 10a and 10b may also be driven to assist the paper inits travel. In any case, the wheels 10a and 10b are preferablymechanically coupled together by a chain, gearing, or the like asindicated by the dot-dash line 22, to insure that the wheels rotatecontinuously and in synchronism with one another without'any risk ofslipping in their relative position with respect to each other.

Fig. 2 shows the periphery of the wheels 10a and 1012 developed into aplane, the raised portions or projections 26a and 2612, respectively,forming a Zig-zag pattern corresponding to the zigzag line to be burnedupon the strip 12, to produce a demetallized or patterned strip as shownin Fig. 4, suitable for direct winding upon a mandrel to produce-aconvolute capacitor unit. As shown in the figure, each patterning wheel10a and 1% has a zig-Zag projection on its periphery 26a and 26b,respectively, the pitch of which varies progressively along the length pof the periphery of each wheel. While other shapes may be used, thezig-zag line conveniently is of rectangular form asshown in the-drawing,i.e. consisting of a line running along one side of the periphery andthen turning at right angles across the width of the peripher-y where itagain turns at right angles along the otherside andthen back .again .tothe first-sideand so on.

The rate of variation of the pitch of the zig-zag line depends on thethickness of the paper and the size of the first electrode (23 or 36,Fig. 4) of the pattern being chosen to suit the periphery of the mandrelon which the capacitor is to be wound, the arrangement being such thatthe successive cycles of the zig-zag path burned away from the metalcoating of the strip will be accurately superimposed on one another inthe wound or finished capacitor. The progression of pitch of the zig-zagline continues from wheel to Wheel, so that if the peripheries of theWheel are developed into a plane and placed end to end, as shown in Fig.2, the pitch of the zig-zag will progressively increase from thebeginning of the first wheel to the end of the last wheel.

In other respects, the wheels are all similar to one another andpreferably of the same size. Each wheel is made of conducting materialand has an insulating bushing so that the wheel peripheries areinsulated from ground or from the frame of the machine. The wheels aregeared together or otherwise mechanically interconnected to insure thatthey always rotate in synchronism with one another. 7

Around the surfaces of the Wheels 10a and 10b and between those surfacesand the metallized strip 12 amask or stencil 23a and 2312, respectively,is arranged, preferably one around each wheel and independently of theother. In the arrangement shown, the mask 23a passes around the surfaceof wheel 10a and around a guide roller 24a in the form of an endlessloop. Similarly, the mask 23b passes around the Wheel 10b and the guideroller 24b. The masks 23a and 23b may consist of insulating strips, suchas paper, symthetic plastic, etc., joined together to form a loop havingopenings 25 cut therein, as shown in Fig. 3 which shows the mask 23adeveloped into a plane. The length l of the opening 25 is arranged to beclosely equal to the periphery p of the. wheels and the width w of theopening 25 is made equal to the width of the patterned surface of thewheels. The slots are so located in the masks, that, as the wheelsrotate, the two ends of a slot will register exactly with the beginningand end of the zig-zag pattern of the respective wheel periphery.Alternatively, if preferred, a single mask may be used with all thewheels instead of one mask for each, such single mask being so arrangedand guided that the single slot reaches each of the wheels in turn atexactly the right moment.

The overall length L of the masks 23a and 23b is arranged to be an exactmultiple of the periphery p of the wheels, i.e. L=np, wherein nrepresents the number of the wheels used. Thus, when using two wheels,as shown in Fig. 1, the patterned surface of the wheels will all beexposed during one revolution and will be entirely covered during thenext revolution and exposed again during the third revolution, and soon.

In other words, with the arrangements shown comprising two patterningwheels, the length L of the mask must be made equal to twice theperiphery p of the wheels, and if three such wheels are used in tandem,the length of the mask should be three times said periphery. With suchan arrangement, when the paper strip 12 is drawn from left to right withrotation of the wheels 10a and 10b and the appropriate voltages appliedbetween the contact rollers or metal coating and the insulating wheels,a continuous pattern, Fig. 4, on the surface of the wheels will be burntinto the surface of the metallization on the paper base equal to that ofthe length of the pattern, starting from the small electrodes andincreasing to the largest required along the length of the metallizedstrip.

Referring more specifically to the arrangement according to .Fig. l, thecut-out portions 25 of the masks 23a and 2312 are advantageouslyarranged in phase orregistry, insuch a manner that thestarting points ofthe patterns 26a and 26b on the wheels Illa and 10b are exposed .insynchronism to the metallized surface of the strip 12, whereby fioeffecta simultaneous burning ofthe respective gnaw patterns or sections uponsequential portions or lengths of the strip and to result in acontinuous demetallized zig-zag line during a single revolution of thewheels a and 10b. During the next revolution, both wheels 10a and 10bwill be covered or masked by the solid portions of the masks 23a and23b, thus advancing the strip 12 by a length equal to the periphery p toa position ready for starting a new patterning cycle, provided thewheels 10a and 10b and the strip 12 are so arranged that the length ofthe strip between successive wheels substantially equals the peripheryp.

In order to provide completely demetallized leader and trailer sectionsat the beginning and end of the complete pattern, the beginning ofpattern 26a and the end of pattern 2612 on the wheels may be providedwith solid projecting portions (not shown), in a manner readilyunderstood.

It more than two patterning wheels are used with the masks having alength equal to n times the periphery p,

as pointed out above, then a length of n times the periphery p of onewheel will be patterned during the first revolution of the wheels, whilethe strip will be advanced by a distance n-l times the periphery pduring the next nl revolutions, to be ready for the next patterningcycle or operation. In this manner, complete electrode patterns, eachcomprising a number of fractional portions or sub-patterns produced by anumber of separate patterning wheels may be produced, each completepattern adjoining the preceding pattern and serving for winding acapacitor of given type or capacitance, in a manner readily understoodfrom the foregoing.

It is also possible to burn the partial or sub-patterns of a completeelectrode pattern in succession, instead of simultaneously, by suitablystaggering the openings in the masks or by a corresponding design of theswitching mechanism controlling the application of the burning potentialto the patterning wheels. In this case, an unburned length is obtainedbetween successive complete patterns which may be completelydemetallized by an auxiliary electrode to serve as clear leading ortrailing sections of the strips wound into individual capacitor units.

Difficulty is sometimes experienced in securing exact synchronismbetween the finish of the partial or sub-pattern of one wheel andcommencement of the sub-pattern of the next. If the space between thepatterns is kept to small limits, it is not very material whether theend of the second sub-pattern falls upon the end of the first or not,provided that the metallization is burned away between the twopatternsto an extent, to prevent it acting as a short-circuit betweenthe electrodes of opposite polarity in the finished capacitor.

Thus, in Fig. 4, which represents a patterned paper strip 12 with thezigzag line 27 burnt in the metallization, leaving successive electrodes28 and 30 of opposite polarity and increasing width starting asindicated from the left-handed side of the strip, the metal coating isshown removed or burnt at the termination of the pattern of the firstwheel at F and before the commencement of the pattern from the nextwheel at G, to leave a free space and to prevent short-circuits betweenelectrodes 28 and 30 of opposite polarity due to lack of completeregistry of the ends and beginnings of the pattern of adjacent wheels.'This can be eiTected by finishing the pattern on each wheel or bybeginning the next wheel by a blank portion or both, as shown at A, Fig.2, which blank portion or portions act to burn away the metallizationentirely to produce a free space H as shown in Fig. 4. Alternatively, aseparate auxiliary electrode may be provided between the main wheels 10aand 10b which serves to burn away the intervening portion H at theappropriate place by control of the electric supply at the appropriatemoment.

As indicated above, if three patterning wheelsare used, the length ofthe masks should be made three times the periphery p of each wheel, butif more than three wheels are required to give a suificient length ofpatterned paper, then, by choosing an even number of wheels, the maskson each of them can be kept down to double the periphery p of a singlewheel and switching means operating in synchronism with the wheels maybe arranged to connect or disconnect the wheels to or from the electricsupply at the appropriate intervals of time. Thus, in the case of fourwheels, the masks and switching device cooperate so that three spacesare left between each section of pattern that is put on by any onewheel, as described in detail hereafter. The switching means may connectthe wheels to the electric supply in turn, so that the pattern comesunto the paper in the desired sequence. 7

By this means, a combination of any desired number of wheels and therequisite switching means, any desired length of metallized paper can bepatterned in such a way that the width of the electrodes left thereonsuccessively increases in an exactly similar manner to that which wouldbe obtained had a single very large pattern wheel been used, theadvantage of a plurality of relatively small wheels in tandem over asingle large wheel being due to the ease of handling the smaller wheelsin the machine and the reduced cost of the manufacture, while achievinga similar result to that of using a single large wheel.

Referring to Fig. 5, there is shown a patterning system of the lattertype, comprising four patterning wheels 10a, 10b, 10c and 10d and aswitching arrangement cooperating therewith to enable the use of masks23a, 23b, 23c and 23d of a length equal to only twice the periphery p ofone of the wheels. Without the switching arrangemengthe length of themasks would have to be four times the periphery p in accordance with thegeneral rule-given hereinabove. In the example shown in Fig. 5, theswitching device 34 comprises arotating contact 35 operated insynchronism with the wheels 10a, 10b, 10c and 10d by theaid of asuitable coupling device 22 and speed-change gear 40 to cause thecontact 35 to rotate at a speed equal to one-fourth the speed of thepatterning wheels. The contact 35 which is connected to the electricsource 16 cooperates'with a segmental stationary contact 37 connected tothe patterning wheels and being so designed as to connect the wheels tothe electric source during one full revolution, corresponding to aquarter revolution of the contact 35, and to disconnect the wheels fromthe electric source during the succeeding three revolutions, or ingeneral n -l revolutions in case of n wheels. For this purpose, theswitch may comprise contacting and insulating segments 37 and 36 havingangular dimensions of and 270, respectively, as shown in the drawing.

The wheels 10a, 10b, 10c and 10d are shown connected to the contact 37of the switching device through a separate resistor 17' with a smallby-pass capacitor 18' connected directly between the connections to thewheels and ground or the frame of the machine. These result in the cleanburning away of the metallized coating on the paper as is well known.

Fig. 6 shows an arrangement similar to Fig. 5 wherein the masks 23a,23b, 23c and 2301' are omitted entirely and control of the patterning bythe wheels 10a, 10b, 10c and 10d is efiected exclusively by the switch34 by connecting and disconnecting the wheels to and from the electricsource 16 at the appropriate time. Again, all the wheels are connectedto the source 16 during one revolution to burn successive sections ofthe pattern and result in a final resultant demetallized zig-zag patternon the strip, this active revolution being followed by three idle orinactive revolutions during which the source 16 is disconnected from thewheels, to advance the strip by a length sufficient to start a newpatterning cycle or operation.

In arrangements according to Fig. 6, where the use of masks is avoidedaltogether and replaced by synchronously operated switching means, itmay be necessary to guide the strip 12 in such a manner that, instead ofbeing wrapped around the peripheries of the wheels, it is brought closeto the periphery substantially at the point only to avoidshort-circuiting of the electrical supply, when switched on, by thecontact of the metal coating of the strip with the wheel periphery. Theguiding of the strip 12 may be readily accomplished by the use ofauxiliary guide rollers 12a and auxiliary pressure rollers 10a, 10b, 10cand 10d. However, this guiding requirement will be unnecessary if thefree or completely demetallized portions at the ends of a completepattern equal or exceed the length of the wrapping arc or angle of thestrip upon the wheels. Otherwise, the function and operation of Fig. 6is substantially similar to that of Fig. 5.

If a different number of patterning wheels are used, the switch 34 is sodesigned as to connect the wheels to the source 16 during one revolutionand to disconnect the wheels during n1 revolutions, the speed-changegears 41 in this case being designed to reduce the speed of the switch34 to l/n times the speed of the patterning wheels, in the case of 11wheels being used in tandem to burn a pattern of corresponding lengthupon the strip 12.

Instead of producing the sub-patterns from the various wheelssimultaneously or consecutively, the patterning cycles by the wheels maybe staggered or interlaced, in which case unpatterned portions betweensuccessive complete patterns may be avoided. An arrangement of this typeis shown in Fig. 7. The latter indicates diagrammatically an arrangementcomprising three patterning wheels Ida, 10b and 10c, arranged in tandemwith the paper web 12 passing over the surface of the wheels,'insubstantially the same manner as in the preceding illustrations. Theelectric source is simply indicated by the plus sign and may be similaras shown in the preceding figures. The switch 34 in the example shownagain comprises a rotary switch arm 35 driven by a chain or otherconvenient form of coupling 22 by the wheels 10a, 10b and ltlcthrough aspeed-change gear 41 designed to cause the switch arm to rotate at aspeed /3 the speed of the wheels 10a, 10b and 100. which are preferablyme: ohanically coupled to rotate in synchronism with each other. Switch4-1, in the example shown, has three segmental stationary contacts 40,41 and 42 each covering substantially an arc of 120 and being spaced byinsulating segments, as shown in the drawing. Contacts 40, 41 and 42 areconnected to the patterning wheels 10a, 10b and 100, respectively,preferably through additional individuallimiting resistors and by-passcapacitors (not shown) similar to those shown at 17' and 18 in 'Figs.and 6.

The operation of the device shown in Fig. 7 is as follows: With thepatterning wheels a, 10b and 100 properly adjusted in relation to oneanother and to the rotating contact 35 and with the latter rotating at/3, the speed of the wheels by the proper design of the speedchange gear40, the sub-patterns upon the wheels will be burned upon the metallizedstrip 12 in succession, in such a manner that at first there will beapplied the subpattern of the wheel 10b during the engagement of thecontact 35 with the contact 40. During the next revolution of the wheelsand engagement of the contact 35 with the contact 41, the sub-pattern ofwheel 10a will be burned upon the strip 12 at a spacing distance fromthe previously burned sub-pattern equal to the length of the periphery pof the wheels, provided the wheels are so spaced or arranged in relationto the strip 12, as to provide spacing distances between successivewheels equal to the periphery p, in a manner readily understood. Duringthe third revolution of the wheels, contact 35 engages contact 42, thuscausing a burning of the partial pattern of the Wheel 1130 upon theintervening space between the patterns previously burned by the Wheels10a and 10b.

As a. result, a complete continuous pattern comprising thesub-patternsof all three wheels will be burned during each successivethree revolution s of the wheels by the proper sequence or interlace ofthe patterns by the switching device 41. Since only one of the wheels isconnected to the voltage source at a time, special masking devices asrequired when the'patterns. are burned simultaneously may be dispensedwith.

In addition to the synchronous switch 41, there is shown in Fig. 7 anadditional switch synchronized therewith and comprising a rotary contact46 and cooperating sta tionary contacts 47, 4.8 and 49 all connected toan auxiliary roller or electrode 50 bearing on the metallized surface ofthe paper web 12. This small. contact roller 5! presses the paperagainst a fixed roller such as 51 and, provided that the position of thecontacts 47, 48 and49 are suitably chosen, roller 50 may'serve to burnaway a portion A, Fig. 2, of the metallization at the junction betweeneach. of the patterns applied by the successive wheels, so as to removeany risk of short-circuit arising should those successive patterns notregister exactly with each other. Variations in the thickness of thepaper tissue, for example, may cause small fluctuations in thepositioning of the, successive sub-patterns necessitating this burningaway procedure between them.

If preferred, this auxiliary roller 50 need only be of a narrow widthcompared with the width of the paper web 12 or of the electrode areaspatterned thereon, and it may also be used to perform a furtherauxiliary function of enabling the capacitance value to be pre-selectedor adjusted within certain limits at difierent values below the totalobtainable by the number of wheels installed on the patterning machine.For example, as is shown in Fig. 8 which represents the end portion ofthe patterning of a paper strip 12 with the zigzag pattern 27 showingsteadily increasing electrode widths from left to right of the diagram,the normal pattern finishes at the point H where the metallization isburnt away completely.

By connecting the auxiliary small electrode wheel 50 to the voltagesupply, which should be separate from the voltage supply for thebranding wheels to prevent shortcircuits, at the appropriate time, astrip 53 will be burnt away on the pattern, to thereby sever theelectrodes 36a, 28a, b, 235 by cutting off therefrom the portions 30a,28a, 38b, 2815, respectively. In this way, the mutual capacitancesbetween the electrodes 30a, 28a 30b and 28b will be entirely lostsincethe remaining portion of electrode 28b will, for example, come oppositeto the cut off portion of b and will therefore virtually have nocapacitance to the other pole of the condenser. Similarly, the cut offportion 2812 will come opposite to the residual portion 39b and thecapacitance thereof which would normally be added to that of the totalcapacitance will thereby be lost. The electrification of this auxiliaryroller 51 in this manner for any desired length of time controlled by asuitable switching'device, therefore provides a ready means of adjustingthe capacitance of the finished condenser wound up from the patternedstrip of metalli zed paper.

Thus, when using a switch like that shown in the drawing, the contactingsegments may be so designed as to burn away a strip 53 of desiredlength, to control the capacitance accordingly. Other switching devicesmay be provided for selective connection to the roller if a differentcapacitance change is required. 7

Referring again to the masking arrangement already described inconnection with Fig. '1, an alternative and sometimes more convenientarrangement, is indicated dia -a.n1matically in Fig. 9. In this diagramthe patterning wheel 19a is provided with projecting pegs or teeth 55,etc., disposed around; its periphery, preferably adjacent to the twoends of the cylindrical wheel. Around these ends and meshingwith thepegs or teeth are disposed two bands 26a and 26b provided with suitablyplaced holes 57a and 57b, respectively. Between these two bands is afurther strip of thin stiff material 58 attached to both of them overwhich a strip 60 of masking material such as of paper, plastic or thelike, is folded at its upper end and attached by any convenient means.This strip 60 will, therefore, be carried around the patterning wheel10a due to the rotation of the latter and by cutting it to theappropriate length it will ensure the exposure to the metallized paperstrip of the pattern on the patterning wheel 10a for the desired lengthof time during 2, 3 or more rotations as selected, depending upon thenumber of patterning wheels installed in the machine.

By this means using the perforated strips 56a, 56!) not only is the mask60 retained in synchronism rotation with the patterning wheel 10a, butthe mask itself can readily be replaced if at any time it is desired toalter its length to suit a change in the number of wheels installed inthe machine, or to replace it after use for a prolonged period of timeduring which it may become mechanically abraded. A simple masking stripof, for example kraft paper of a few mils thickness is readily attachedto the strip 58 and provides a convenient form of mask for this purposeand one which is readily renewable at negligible cost.

It will be appreciated from the description given above that if it isdesired to vary the capacitance of the condenser to be wound up from thestrip of patterned metallized paper, the number of wheels installed inthe machine can be altered as desired, for example, if four wheels areused a total capacitance of approximately three-quarters of the maximummay be obtained by reducing the number to 3, or of approximately halfonly of the capacitance by reducing the number to 2. Adjustment of thecapacitance value intermediate between these major steps can be obtainedby means of an auxiliary contact roller 50 as indicated and describedalready in connection with Figs. 4 and 6.

It will be appreciated also that, in lieu of a separate mask or maskingstrip for each of the patterning wheels, a common mask travelling aroundall of them in turn may be used provided that its length is suitablyadjusted to the number of wheels and the length of strip to bepatterned.

Furthermore, any or all of the masks may have a plurality of openings,but in general a single one is usually to be preferred, particularly ifused in combination with the electrical switching means. When themasking arrangement of Fig. 5 is employed, a single opening is normallyonly obtained, this opening representing the difference in lengthbetween the actual masking strip used and the length of n times theperiphery of the patterning wheel where n represents the number ofwheels in use in the machine at that time.

While there are above disclosed a limited number of embodiments of thestructure, process and product of the invention, it will be evident thatmodifications and variations, as well as the substitution of equivalentelements and steps for those disclosed for illustration, may be madewithout departing from the inventive concept herein disclosed anddefined in the appended claim, and it is desired therefore that thespecification and drawings be regarded in an illustrative rather than ina limiting sense.

Having thus described my invention, I claim:

in a wound electrical capacitor formed of a single metallized insulatedstrip, a linear wavy non-metallized pattern running along the length ofsaid strip and disposed inwardly of the marginal edges thereof providingsuccessively disposed electrode areas of opposite polarity alternatelyand selectively connected to the marginal edge portions of said stripand of progressively increasing extent sized to be located one above theother in mutual capacitive relation in the final convolute winding ofsaid strip and a relatively narrow non-metallized line extendinginwardly from the end of a complete electrode pattern substantiallyequidistant from the marginal edges of said strip and having a length soas to selectively intercept adjacent electrode areas and therebydecrease the effective transverse extent of said areas when the same aredisposed in overlaying mutual capacitive relationship in said woundunit, whereby the longitudinal extent of said relatively narrownon-metallized line provides a Vernier control of the capacitance of thewound unit.

References Cited in the file of this patent UNITED STATES PATENTS2,139,453 Linder Dec. 6, 1938 2,216,558 Ortlieb Oct. 1, 1940 2,390,784Drobish et al. Dec. 11, 1945 2,597,511 Mellen et al May 20, 19522,637,766 Grouse May 5, 1953 2,727,297 Fralish Dec. 20, 1955

